Multipartite Entanglement and Quantum State Exchange

We investigate multipartite entanglement in relation to the theoretical process of quantum state exchange. In particular, we consider such entanglement for a certain pure state involving two groups of N trapped ions. The state, which can be produced via quantum state exchange, is analogous to the steady-state intracavity state of the subthreshold optical nondegenerate parametric amplifier. We show that, firstly, it possesses some 2N-way entanglement. Secondly, we place a lower bound on the amount of such entanglement in the state using a novel measure called the entanglement of minimum bipartite entropy